All known natural calcitonin peptides contain an amino acid sequence of 32 amino acids, and have a disulfide bond connecting the cysteinyl residues at positions one and seven. The natural calcintonins include the salmon, eel, bovine, procine, ovine, rat and human calcitonins. Salmon calcitonin, for example, has the following formula: ##STR1##
In U.S. Pat. Nos. 3,926,938, 4,062,815, 3,929,758, 4,033,940, 4,336,187, 4,388,235 and 4,391,747 are disclosed improved syntheses of calcitonins including the salmon calcitonin referred to above.